Coaxial cable



sept. 26, 1961 o. A. MANNELLA 3,002,047

coAxIAL CABLE Filed Oct. l5, 1959 ,United Scare Patent 3,002,047 COAXIALCABLE Orlando A. Mannella, Forest Park, Ill., assignor to Amphenol-BorgElectronics Corporation, Broadview, Ill f a corporation ofDelaware`Filed Oct. 15, 1959, Ser.No. 846,696 4 Claims. (Cl. 174-124) 1 Thisinvention relates to radio Yfrequency transmission lines. Morespecifically, it relates to an improved type of coaxial cable capable ofcontinuous dependable service at extreme temperatures or underconditions of intense nuclear radiation, yet quite exible and with ahigh degree of flexing endurance.

The specific form of cable here disclosed has been demonstrated, byactual test, to be capable of continuous operation at 1000 F. ambienttemperature with satisfactory attenuation and VSWR characteristics; withno perceptible deterioration or change in insulation resistance evenafter 20,000 cycles of bending over a mandrel ten times the diameter ofthe cable under test. No other cablepresently available to the industryaccomplishes comparable performance.

It is thus the primary object of the present Iinvention to provideaunique and improved coaxial line capable of continuous operation underambient temperatures in the 1000 F. range and also cabable ofwithstanding thousands, of cyclesfof bending'without unduedeterioration, particularly as to the breakdown voltage or insulationresistance of the cable dielectric. The manner in which the foregoingobjects are accomplished will be described in greater detail inconnection with the drawing attached to and vforming a part of thepresent specification wherein:

FIGURE 1 is a detail side elevational view of a portion of thetransmission system described hereinafter, with the outer jacket and thesuccessive layers of which the line is formed shown cut back toillustrate the details of construction thereof; and

FIGURE 2 is a sketch of a sealed radio frequency transmission systemconsisting of a length of the unique line shown in FIGURE l, extendingbetween a pair of connector ttings.

As will be observed fromFIGURE l, the basic parts of the line are thecentral conductor 10, which is surrounded by a semi-solid silicadielectric 11 andra tubular outer conductor 12. The dielectric 11preferably consists of plural layers 13, y14, 15, 16 and 17 of berglass,eachV in the -form of a continuous coaxial sheath around the centralconductor. 'Ihe parts 10 and 11 thus comprise a core closely encased inthe outer conductor 12 of braided wire and surrounded by a jacket 18consisting of a flexible hose of stainless steel. The opposite ends ofthe stainless steel jacket 18 are brazed to terminal connector fittings19 and 20, each of which have dielectric inserts hermetically sealed inthe connector shells so that the entire unit functions as a sealed radiofrequency transmission system.

In the present preferred commercial embodiment of the cable, whichis'designed to have a characteristic impedance of 50 ohms, the centralconductor 10 consists of seven strands of American wire gauge size 21,silver covered copper wire. The nominal diameter of each strand of thisWire is .0285 inch, whereby the inside conductor has a nominal diameterof .085 inch with a lay of .7 to 1.3 inches. The fiberglass core is madeup of a major portion (substantially 55% of the strands) of yarn formedof fiberglass bonded staple sliver 22 (identied in the industry asESD-E-lO), with a minor portion (45%) of continuous filament berglassyarn. In the preferred construction, this includes about 18% of thestrands 23 of filament identified as ECG-150-4/4 and about 27% of thestrands 24 identified as ECG-150 1/10, 8 ends. For

Patented Sept. 26, 1961 2 optimum results, the inside layers 13, 14, 15and 16 of the dielectric are each woven with twelve strands 22 of thestaple berglass, interwoven with four strands 23 of the continuousfilament fiberglass to give a major portion of 75% staple iiberglass and25% continuous lament fiberglass in the innermost layers, while theouter layer 17 is formed of twenty-four strands 24 of continuous`filament ber. This results in tive coaxial sheaths of progressivelythinner layers of braided dielectric, with the wall thickness of theinside sheath 13 being greatest and the sheaths 14, 15, lloand 17progressively less.

VAftertheV sheaths 13-17 are braided, the line is subjected to hightemperature baking, preferably for a period of at least an hour, and ata sustained temperature of at least 900 F. The outer tubular conductor12 off the line is then applied. Y As illustrated, the outer conductorconsists of a laye' ofmetallic braid formed of 168 strands of No. 32American wire gauge silver-plated copper wire, in 24 carriers 'of sevenstrands each. The wire of both theinner and outer conductors shouldpreferably be of oxygen-free, high conductivity copper and free of oilor other Aforeign matter. The line is then drawn through a sizing dieand dried overnight at a temperature of 300 or 400 F., after whichindivdual lengths of the cable are mechanically pulled throughcorresponding lengths ofstainless steel hose 18. End connector ttngs 19and 20 are brazed t the hose to close the ends of the sealed system..

'- .f As lindica-ted in. the introduction to the present dis-v closure,there are many and varied instances in which extremely high temperaturecoaxial cables are needed in connection with jet aircraft, guidedmissiles, rockets and many variations of nuclear'installations, yetthere has not heretofore been developed a transmission line capable ofsatisfactorily withstanding such temperatures and still possessing thedegree of flexibility and mechanical endurance necessary to withstandrepeated cycles of iiexing or extreme vibration. It has been learned,however, that coaxial transmission line constructed as described aboveis superior in high temperature perform-ance to any ilexible lineheretofore available to the industry and that, when constructedaccording to the specifications here given, it is quite practical toachieve a high degree of ilexibility and flexing endurance greatlyexceeding normal requirements, yet to also maintain satisfactoryinsulation resistance and breakdown voltage characteristics even aftercontinued ilexing at these elevated temperatures. This is accomplished,moreover, with a cable construction having very satisfactorycharacteristics as to voltage standing wave ratio and attenuation.Further, it has been discovered that while neither staple filamentii-berglass nor continuous filament iiberglass have shown themselves tobe capable of forming a cable dielectric achievingthe desired results,yet the combination of these two types of glass iibers, in Itheproportions and placement here discharacteristics without a compromiseof electrical, physiv cal or mechanical requirements, and thus resultsin a gable having properties not obtainable with either fiber one.

Having thus described my invention, what l claim as new and desire tosecure by United States Letters Patent l. A high temperature radiofrequency transmission system comprising an airtight iiexible metallicjacket of corrugated stainless steel hose extending between a pair ofterminal connectors and hermetically sealed thereto, together with aexible coaxial transmission line interconnecting said connectors andhoused within said jacket; the coaxial line consisting of a centralconductor of stranded flexible wire, an outer tubular conductor of highconductivity woven metallic wire braid, with the central V andsouterconductors .heldin coaxial-spaced relation to each other by a semi-solidsilica dielectric resistant to temperaturesof l000 F. and resistant torepeated bendingfsaid dielectric consisting of aplura1ity'of-continnousAsheaths fof braided fiberglass: yam surroundingreach other andatiordingplural dielectricvlayers betweenthewcentral f Vandsouterconductorsgfwithseach of theinteriolsheaths composed substantially? 5%kof yarn consisting of bonded `staple sliver berglass and 25%-ofyarnconsisting ofgconi v`tinuous Vfilament: vfiber-glass, vand the011terlsheath consist ingorf' continuous filament ber-glass.

t CS2. Ahightemperature radiofrequency transmission system comprising anairtight flexible jacketextendingbetween a pair fof terminal connectors@and ihermetically .sealed thereto; 'together with a vflexibleY coaxialtransmission-:line interconnecting said :connectors andfhousedlwithinrsaidrjaclget; the coaxial lineconsistlng of azcentral conv.dnctor of flexible wire and'4 an' outer 'tubular conductor heldincoaxial spaced relationtoeaclrotherby assomisolid vsilica dielectricresistant totemperatures .of-.1000 F. `and resistant to repeatedbending;fsaid'.dielectric-consiso `ing 1 of braided fiberglass yarnicomposed substantially 5.5%.,01? yarnv consisting ofstaple fberglassand 45% of yarn consisting of filament berglass.

3.` A ii-exible high' temperature vcoaxial'fradio:frequency transmission,line consisting of alcentralv conductorfof stranded exible wire andanoutertubular conductor di highjconductiyity Wovenmetallicwirebraid,`with the central and outer conductors heldgincoaxialfspaced res lationto each other by asemi-solidsi-licadielectric re.-

sistant to temperatures of 41.(l0(}".`r"`. andresistant tore- Ypeatedbending; said dielectric consisting offs-aiplnralityof continuoussheaths of Abraidedviberglass yarn surrounding each other and affordingplural dielectric layers bel Itween the central and outer conductors;with each of the interior sheaths composed substantially 75% of yarny.consisting of ybonded staplefsliver iberglass and 25% of yarnconsisting of continuousilament fiberglass, and the sheaths composedsubstantially 75% of yarn consisting l of staplev berglass and-25% ofyarn consisting of lament fiberglass, land lthe Vouter` sheathvvconsisting of fila-` ment berglass. Y

References Cited in the-leofthispatent' ,Y

UNITEDl STATES vvPA'EIKFS 2334560 t Keyes ivntrx1:1.'1941Y '=2,6s9,695Birdv -Feb.v1'6, '1954 A FOREIGN PATENTS slaan; Netherlands s jnec.v15,1934 .'OTHERIREFERENCES l v 'Wire and Wire Products (publication),November 19.46, {pages`f885-'888 Zandt-9110.

